These fabric expansion joints have certain advantages in the connection of the ends of large conduits usually designed to convey gases, sometimes accompanied by solid particles. For example, they may carry the combustion discharge from a heating fire to apparatus designed to remove noxious vapors and solids prior to discharging the remainder to the atmosphere.
The conduits used for this purpose are metallic and usually large. The fluids passing therethrough are subject to variations in temperature causing expansion and contraction of the conduits; hence there is variation of the space between the ends of conduits which must be connected. A desirable way of connecting the ends of such conduits is by way of a flexible belt usually comprising a plastic fabric or unwoven material, but sometimes utilizing a metallic belt of woven material such as asbestos or the like. In the past such belts were first directly connected to the peripheries of the conduits by bolting or other fastening arrangements.
The difficulties encountered with this arrangement are due to unusually high temperatures of the materials being conveyed in the conduits which rapidly deteriorate many materials which would otherwise be highly desirable for use in such connecting belts. In the past attempts have been made to protect such belting by placing a plurality of layers of temperature resistant material between the open ends of the conduits and beneath the interior surface of the belts but this greatly increases the cost of the joint and frequently still does not solve the problem.
An example of this kind of expansion joint is shown in U.S. Pat. No. 3,460,856 wherein the outer belt is protected by a plurality of layers of material such as woven asbestos cloth protected by metal mesh covering material and supported in a suspended position by fingers. Not only is the use of such complex arrangement expensive but it does not solve the problem of unduly heating the portions of the outer belt, particularly in the areas of connection with the conduits where such heating causes great damage to the outer belt.
The present invention eliminate all of this complexity in a simple fashion. The outer belt, which may comprise one or more layers is suspended away from the open ends of the ducts with a baffling arrangement comprising overlapping axially spaced baffle members. This not only greatly improves the joint by way of simplification but also substantially reduces the temperature at the inner surface of the belt and particularly at its connecting points.
There is not only the heat problem which these expansion joints have to contend with. Continuing the combustion discharge analogy this material from the fire contains solids such as fly ash. These expansion joints extend completely around the conduits, which are usually squarish thus roughly three quarters of the joint is exposed to gravitational forces; this is roughly the bottom and the sides. Solid particles in the combustion fluid, such as fly ash, tend to impinge on the joint and be caught there, thus building up an accumulation of such solids. This is so even where the surface of the belt in the joint is substantially contiguous with the surface of the conduits as shown in the joint of U.S. Pat. No. 3,552,776. In that joint there is no obstruction to impingement of the solids and deterioration of the belts. Even with the baffle shown in U.S. Pat. No. 3,460,856 there is an opening between the baffle and the downside of the joint. In such structure there is a tendency for these solid particles to entrap the space between the baffle and the belt.
In the construction of the present invention the incoming material from the up-stream conduit is diverted by the baffling arrangement. As it flows by the opening between the two baffles, some of it is diverted upwardly and through the opening between the baffles and eddy currents are set up which tend to whirl through the space between the belt and baffles. The whirling action of these eddy currents keeps the solid particles alive and whirling around with the gases. They eject with the ejecting fluid and hence the joint is constantly cleansing itself of these solids. Also, the spacing of the belt from the main stream in the conduits and the whirling action referred to substantially reduces the temperature of the material contacting the belt. It should also be pointed out that because the opening between the baffles is down stream there is less tendency for the fluids and solids to reverse direction and flow into the space between the baffles and the belt. The material that does so flow moves slowly and therefore has more time to cool before contacting the belt.
An object of the present invention is to provide an expansion joint for the ends of conduits carrying hot fluid gases containing solid particles which will withstand high temperatures and inhibit the deposition of the solid particles within the joint structure.
Another object of the present invention is to provide an expansion joint which may utilize successfully flexible material unable to withstand temperatures of the gases flowing through the conduits if they came in direct contact with such gases.
Finally it is an object of this invention to provide a fabric expansion joint which has all the advantages innate in such joints and yet may utilize materials which would deteriorate rapidly if used in various prior art structures.
Other objects, advantages and salient features of the present invention will be apparant and readily understood from the following description of the invention: